'Subject' says it all.  A recent response in a post indicated that radiant floor heating is not good in ICF structures, and unfortunately (?), that is what is installed in the ICF home I am building.  What is wrong with the combination? 

What did the recent response you are talking about state as the reason that icf and radiant don't mix well?  In certain locations it might not do well with radiant as it is a gradual heating system, not as quick as other options.  So in florida for example I would not suggest it.  But with an ICF home as the only reason, I would not agree with that at all.  I know 4 people in Colorado, 3 seperate homes that are icf and they have radiant and love it.  I've visited and it was a very comfortable home. 

My opinion is that radiant hydronic and ICF are the perfect combination, but there are some things to be aware of at the design stage.
One is that a solid ICF wall will enable the house to respond very slowly to changes in conditions outdoors. Fine, the radiant hydronic responds slowly to control inputs too. So far, so good - they are quite compatible.
Second, having a lot of glass area will speed up the response time indoors to changes outdoors but do nothing for the response time of the heating system. Not so good - the lag could lead to indoor temperatures either too high or too low.
There are solutions to be found with sophisticated control systems. Somebody who understands them can explain them to you. I can't.
One of the things I did in my own ICF house (basement plus two stories) was to install baseboard convector heat delivery on the top floor and radiant on the other two. I have a quick responding heating system where most of the heat is lost and warm feet where we spend most of our time. There is a good deal more to it than that, but that was a big step toward a solution, and, rather than increasing the cost of the job which the control ystems would have, actually rduced the cost.
If that is not an option for you, you will have to check out controls that account for outdoor temperature changes.

That's silly. Absolutely Nothing!

Thanks to the three of you for your responses which all reinforce my feeling that it is a good combination where my home is in inland Northern California where winters stay cool w/ a need for constant heating (and rare warmer periods can be dealt with by the newfangled means of 'opening a few windows') and sjmmers stay warm so the heating is turned off. I think I'm good to go....

The area is the only problem with radiant floor heating. Here in Tennessee, it maybe 0 one day and you crank up the heat. It will take 8 to 10 hours to get up to temp. then 3 days later it is 65 and you have to open the windows. Radiant floor heating is a great system for a cold area.